Reserve for Future Policy Benefits and Contractholder Funds - Schedule of Rollforward of Reserve for Future Policy Benefits (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Present value of expected net premiums
Beginning balance	$ 2,013	$ 1,702
Beginning balance at original discount rate	2,067	1,795
Effect of changes in cash flow assumptions			$ (101)	$ 22
Effect of actual variances from expected experience			32	0
Adjusted beginning balance			1,998	1,817
Issuances	559	431
Interest accrual	74	56
Net premiums collected	(330)	(297)
Ending balance at original discount rate	2,301	2,007
Effect of changes in discount rate assumptions	5	(132)
Reclassified to liabilities held for sale	(1,615)	0
Ending balance	691	1,875
Present value of expected future policy benefits
Beginning balance	3,110	2,753
Beginning balance at original discount rate	3,151	2,850
Effect of changes in cash flow assumptions			(21)	51
Effect of actual variances from expected experience			(32)	(21)
Adjusted beginning balance			3,098	2,880
Issuances	548	436
Interest accrual	107	93
Benefit payments	(341)	(327)
Ending balance at original discount rate	3,412	3,082
Effect of changes in discount rate assumptions	35	(164)
Reclassified to liabilities held for sale	(2,702)	0
Ending balance	745	2,918
Net reserve for future policy benefits	54	1,043
Less: reinsurance recoverables	0	84
Net reserve for future policy benefits, after reinsurance recoverables	54	959
Reserves related to short-duration contracts	220	266
Accident and health insurance
Present value of expected net premiums
Beginning balance	1,688	1,464
Beginning balance at original discount rate	1,737	1,549
Effect of changes in cash flow assumptions			(88)	(12)
Effect of actual variances from expected experience			28	(4)
Adjusted beginning balance			1,677	1,533
Issuances	490	378
Interest accrual	63	48
Net premiums collected	(281)	(260)
Ending balance at original discount rate	1,949	1,699
Effect of changes in discount rate assumptions	6	(113)
Reclassified to liabilities held for sale	(1,270)	0
Ending balance	685	1,586
Present value of expected future policy benefits
Beginning balance	2,453	2,229
Beginning balance at original discount rate	2,495	2,316
Effect of changes in cash flow assumptions			(11)	21
Effect of actual variances from expected experience			(28)	(24)
Adjusted beginning balance			2,456	2,313
Issuances	479	368
Interest accrual	84	75
Benefit payments	(317)	(297)
Ending balance at original discount rate	2,702	2,459
Effect of changes in discount rate assumptions	27	(126)
Reclassified to liabilities held for sale	(1,998)	0
Ending balance	731	2,333
Net reserve for future policy benefits	46	747
Less: reinsurance recoverables	0	82
Net reserve for future policy benefits, after reinsurance recoverables	46	665
Traditional life
Present value of expected net premiums
Beginning balance	325	238
Beginning balance at original discount rate	330	246
Effect of changes in cash flow assumptions			(13)	34
Effect of actual variances from expected experience			4	4
Adjusted beginning balance			321	284
Issuances	69	53
Interest accrual	11	8
Net premiums collected	(49)	(37)
Ending balance at original discount rate	352	308
Effect of changes in discount rate assumptions	(1)	(19)
Reclassified to liabilities held for sale	(345)	0
Ending balance	6	289
Present value of expected future policy benefits
Beginning balance	657	524
Beginning balance at original discount rate	656	534
Effect of changes in cash flow assumptions			(10)	30
Effect of actual variances from expected experience			(4)	3
Adjusted beginning balance			$ 642	$ 567
Issuances	69	68
Interest accrual	23	18
Benefit payments	(24)	(30)
Ending balance at original discount rate	710	623
Effect of changes in discount rate assumptions	8	(38)
Reclassified to liabilities held for sale	(704)	0
Ending balance	14	585
Net reserve for future policy benefits	8	296
Less: reinsurance recoverables	0	2
Net reserve for future policy benefits, after reinsurance recoverables	$ 8	$ 294